INTRO The Prussian Enclave, a small territory by the Baltic Sea, has been threatened by great neighbours from time immemorial. People settling here used this protection and over time many defensive devices were developed and constructed. The building of defensive devices has taken place from ancient times when the on the grounds of historic Prussia. Prussians have used geography, forests, swamps and lakes for defence for a long time as a way of limiting access to this area. One form of early protections included the building of defensive wooden settlements on the many shallows of the Mazurian Lakes (Orzysz, Szostak, Woszczele). During the 5th century Baltic-tribes unrolled new manners of defences on these ancient grounds. Villages, so-called "Lauks", located in the difficult and inaccessible places, building houses in defensive circles. On truncate hills and artificially heaped up mounds were located fortified castles with palisades and moats (Jeziorko, Tolkmicko, Ostrow, Tyrklo, Grodzisko, Cisowy Jar), which protected the neighbouring populations in times of war. Other manners of protection included in the greater territory were 5-20 km field ramparts (Barczewo, Mlynary, Zimna Woda), similar to Polish defensive ramparts in Silesia. After the conquest of Prussia, German Teutonic Knights raised brick- stone and wooden castles, located often on places of former Prussian castles. The most important Teutonic castles were in Warmia & Mazury area: Malbork - Marienburg, Olsztyn - Allenstein, Lidzbark - Heilsberg, Nidzica and the cathedral complex in Frombork. In the 14th & 15th centuries the Germans extended gradually and adapted their own castles to new needs (artillery, fire-arm). These powerful fortresses, earthworks and bastion fortifications saved the Teutonic Knights State before complete extermination in numerous wars against the Polish Kingdom. Increasing powers of the Prussian Kingdom first appeared in 18th century through the controll and blocking of waterways leading from Poland to the Baltic Sea. In times of the so-called "Wars for Customs Duty", the Germans built modern fortresses: near the Vistula River in Grudziadz (Graudenz 1776-90), "Fort Lyck" on Czarci Ostrow Island on Sniardwy Lake (1784-88) and the six-forts fortress of Pilawa-Baltijsk by the Baltic Sea.
In 1816 General Grollmann proposed the fortifying of the Gizycko (Lötzen) defile. He built the new bastion-polygon "Fortress Boyen", completed in 1844-56. More modern fortifications were built by the Germans in Koenigsberg (Kaliningrad) city and port. In years 1874-90 came into being powerful, the ring of 12-fort fortress, covering with field - fortifications near the Dejma and Frisch Rivers. The Germans, in 1900-05, fortified bridges and railway viaducts, and built double and single HMG-towers, blockhouses and guardhouses including (Samborowo, Jablonowo, Biesal, Ilawa, Ostroda, Mikolajki, Ruciane). 19th century fortifications near Vistula River with new fortifications from 20th century formed "Vistula Line" with fortresses Torun - Thorn, Chelmno-Culm, Grudziadz, Malbork-Marienburg and Wisloujscie Gdansk-Danzig. During the period of 1914-45, the East Prussian "Fortress" was used extensively and can be said to have reached it's most powerful position. At the end of WW II these concrete fortifications fell in battles against Russian tanks and soldiers. The remaining structures have come to determine a lively history of this region. Today, the northern part of the former East Prussia is still a military "fortress" and is considered to be an important strategic area (the Russian Kaliningradskaya Oblast).